1. The Field of the Invention
The present invention relates to a method and apparatus for using seismic antennas to illuminate subterranean features for display and evaluation, and in particular to a new and novel approach to this problem utilizing continuous wave techniques.
2. The Prior Art
The seismic method, as practiced today, takes advantage of many elements of basic earth physics. There are, however, some basic physical principles and techniques that are not actively pursued in the current 3D and Common Depth Point based seismic methodologies. The present invention investigates what different combinations of sources, receivers, processing and display parameters could take advantage of some of the other elements of physics which we are not currently emphasizing. For example, interferometry is a technique which has been utilized in other branches of science for many years. It has not been routinely applied to the acquisition of seismic data to date because the current techniques of seismic data acquisition and processing do not favor the method. Interferometry is a technique that could yield directional data in a way significantly different from the current 3D or CDP methods. It would require consideration of different sources, receivers, processing methods and parameters.
A relatively new technique developed in the science of radio and optical astronomy is the procedure of non-redundant masking. This computer-intensive procedure has been shown to dramatically increase the signal to noise ratio and the angular resolution of the data by a factor of twenty.
Consideration of these two concepts, and development of the resulting ideas, has led to the definition of a potentially useful new system of acquiring, processing and interpreting seismic data. In essence, the subject method proposes to "illuminate" a region of subsurface with long duration monofrequency seismic signals of known characteristics and location. The reflections of these signals would then be detected by a highly direction-sensitive antenna array. Full-wave, three-component signals would be recorded at each antenna element of the array. The source would be moved from place to place to create a 3D illumination of the region. The data would be processed to remove unwanted noise and to increase signal strength. Computation of the 3D velocity field of the Earth filter would allow the correct interpretation of the overall dataset.